1. Field of the Invention
The present invention relates to a printer optical scanning apparatus and a color printer optical scanning system using the apparatus, and more particularly, to a printer optical scanning apparatus that appropriately controls the image information scanning time of an optical scanning unit in response to latitudinal movements of a photoreceptor belt in a direction perpendicular to a proceeding direction of the photoreceptor belt, and to a color printer optical scanning system using the apparatus.
2. Description of the Related Art
FIG. 1 shows a general printer. In the printer, a photoreceptor belt 14 circulates in a direction indicated by the arrows around three rollers 11, 12, and 13. A resetter 15, optical scanning units 30, developing units 17, a drying unit 18, and a transferring unit 20 are arranged near the circulating path of the photoreceptor belt 14 and are spaced a predetermined distance apart from one another.
In a printing process, the optical scanning units scan rays of light to the photoreceptor belt 14, circulating via the resetter 15. An electrostatic latent image is formed on the photoreceptor belt 14 by the scanned rays and then developed by a developer supplied by each of the developing units 17. A color image is formed by the optical scanning units 30 and the developing units 17, respectively scanning rays of different color information and performing development using developers corresponding to the scanned colors.
As the photoreceptor belt 14 continues to circulate, the color image formed on the photoreceptor belt 14 passes the drying unit 18 and is transferred to a transfer roller 21 that is rotating such that a part of the roller is engaged with the photoreceptor belt 14. The image that is transferred to the transfer roller 21 is then transferred to a sheet of paper 23 which passes between the transfer roller 21 and the press roller 22 which are engaged with each other and rotate to advance the paper 23.
In a printer operating as described above, four optical scanning units 30 are spaced with each other in order to display a color image and scan color information corresponding to yellow, magenta, cyan, and black, respectively.
Each optical scanning unit 30, one of which is shown in FIG. 2, is comprised of the same components. Referring to the drawing, the optical scanning unit 30 has a light source 31, a rotary polygonal mirror 32, a motor M, and a lens unit 33.
An optical scanning apparatus includes the scanning unit 30, an optical scanning controller 35, and a photodetector 34. During the operation of the optical scanning apparatus, the photodetector 34 detects the scanned light, from a position beyond the photoreceptor belt 14 and the edge of the photoreceptor belt 14, among the light rays output from the optical scanning unit 30, and outputs a corresponding pulse signal to the optical scanning controller 35. A scanning start instructing portion 36 of the optical scanning controller 35 determines a falling edge of the input pulse signal when the scanned light arrives at the edge of the photoreceptor belt 14. The scanning start instructing portion 36 then outputs an image information scanning start signal to a scanning controlling portion 37 after counting the optical scanning time corresponding to distance a from the edge of the photoreceptor belt 14 to a set image information recording area D. The scanning controlling portion 37 drives the light source 31 such that an optical signal, corresponding to image data, is output after being synchronized with the scanning start signal of the scanning start instructing portion 36.
However, in the conventional optical scanning apparatus described above, because the paper is always loaded to the same position, when the photoreceptor belt slips from its normal path, the image position to be transferred to the paper is moved in an amount corresponding to the slipping distance of the photoreceptor belt. As a result, a desired arrangement of a print image on a paper cannot be obtained.